Doors of the type herein contemplated, such as those used on coke ovens, are removable from their door frames to facilitate the emptying of the corresponding coking chambers, e.g. as described in commonly owned patent application Ser. No. 651,777 filed Jan. 23, 1976 by one of us, Karl Gregor, jointly with Kurt Asmus, now U.S. Pat. No. 4,153,515. After the door and its frame have been separately cleaned, the door-removal device is operated in reverse to re-emplace the door on the frame to which it is then again latched.
The latch arms used for this purpose, when in an operative position, are under axial pressure of spring means--usually a stack of Belleville springs--urging their extremities into frictional engagement with respective lands on the door frame. The pivot stud is surrounded by an axially shiftable thrust member, usually of annular shape, which has an inward extension or skirt contacting the stack of Belleville springs to relieve their pressure when the thrust member is repressed, thereby allowing the latch arm to be swung out of engagement with the coacting lands of the door frame. Such repression is performed by an unlatching head supported on the body of the door-removal device after the latter has been advanced from a withdrawn position into a working position by hydraulic drive means anchored to that body and to an associated base. The base may be designed as a carriage movable along a coke-oven battery to align the door-removal device with the door frames of the several coking chambers, as also described in the aforementioned commonly owned U.S. Pat. No. 4,153,515.
Since a hydraulic jack serving as the drive means for the advance and withdrawal of the door-removal device generally does not have the power required to release the latch arm or arms of a coke-oven door aligned therewith, the unlatching head is provided with a separate power source. Heretofore, that power source has been a supply of pneumatic pressure operable to engage respective parts of the unlatching head, namely a gripper element and a pressure element, with an outwardly projecting tip of the pivot stud, designed as a knob, and with the surrounding thrust member. These conventional unlatching heads have separate pneumatic pistons and cylinders for the repression of the thrust member during door removal and for the reverse motion during relatching upon re-emplacement of the door.
The use of compressed air as the pressure fluid in such a device allows the spent fluid to be simply discharged into the atmosphere. Since, however, the displacement of the device itself on its base is generally performed by hydraulic drive means, it would be more convenient to operate the unlatching head or heads also by hydraulic fluid. The mechanical and fluidic problems encountered in such a case, however, have not been satisfactorily solved heretofore as far as we are aware.